Positive Displacement Meter Installation, Commissioning and Calibration in the Field

Installation

General System Configuration• A proper metering

system for positive displacement meters should include the following elements:

A strainer with an appropriate mesh basket for the application

An air eliminator The meter A control valve

General System ConfigurationPumping Systems

• The metering system piping must be designed in such a way as to exclude air.

Make sure there are no “pockets” in the piping where air will collect.

Assure that the pump suction is always flooded (positive head condition)

Installation of the metering system

When to install the meter and accessories• The metering system

may be installed after the header system is hydro tested and completely flushed.

• The piping system must be clean and free from dirt, rust and pipe scale before installing the metering system.

Installation of the metering system

Support the meter and accessories• Assure the meter is securely

bolted to its riser or foundation.

• Support the strainer/air eliminator and the valve with appropriate stand-offs.

• Support the inlet and outlet piping.

• Make sure none of the metering system components are subjected to pipe strain.

Commissioning

Here are some examples of system problems to be avoided

• Manual valve actuation causing rapid starts and stops.

• Perhaps one of the worst cases occurs in systems with “snap action” valves. These valves are intended for safety requirements but end up being used by operators to control the system.

Here are some examples of system problems to be avoided

• The metering system is subjected to rapid product temperature changes.

• Other equipment not associated with the meter but in a branch connection to the system is started or stopped causing pressure and/or velocity “spikes”.

Here are some examples of system problems to be avoided

• Drain back in gantry headers occurs as the supply tank level drains below the header level. NRV’s that do not hold allow air into the system.

• Severe instances can cause a suction in the header causing air eliminators to drop allowing additional air into the system.

Here are some examples of system problems to be avoided

• Starting the gantry pumps with the valves between the meters and the pumps fully opened.

• The resulting hydrodynamic shock pressures and velocities will likely cause damage to any metering system.

• System valves must be kept closed as the pumps are started and the system pressurized slowly

Metering System OperationThe first time the system is

operated

• Filling the system slowly. • Bleed the air off of the

meter and the control valve.

Caution !• Very long systems may be difficult to bleed

off all of the air. Take precautions to assure that all air is removed from the system before beginning deliveries or operating the system at full flow. Failure to take the necessary precautions can result in a condition called “spinout” which is caused by rapidly expanding slugs of air.

Initial operation• When all of the air is gone

and the system is full of product, the unit is ready for initial operation.

• After successfully starting and stopping flow with no transient pressure problems, the system is ready for calibration

Calibration

Linearity and Repeatability

• The 5:1 turndown ratio has the most narrow linearity range, +/- .15%

• The 10:1 turndown ratio has a linearity range of +/-.22%

• The 20:1 turndown ratio has a linearity range of +/-.50%

• Repeatability is .05%

Calibration, Practical Aspects• Volumetric proving is defined as

filling a tank of a known volume at various flowrates. Multiple “proving” runs are taken at each flow rate to establish linearity and repeatability.

• Volumetric provers are considered primary standards and when used with proper temperature and pressure measurement achieve “standard volume measurements”.

Volumetric proving• Proving techniques are well defined by

organizations such as the American Petroleum Institute (API).

• Here are some important proving issues:The meter must be thermally stable before

the prover runs are made. Run the meter to assure it is at the same temperature as the product.

Volumetric provingKeep the meter to be proven as

close to the prover as is possible. This minimizes temperature differences between the meter under test and the prover.

Volumetric proving• Volumetric proving requires temperature

measurement at the prover and in the process line adjacent to the meter under test.

• It also requires system pressure readings taken during the proving run.

• These measurements allow the calculation of a base temperature volume.

Master Meter Proving

• The master meter is simply a meter that has been proven against a primary standard. We select meters that have the best repeatability.

Master Meter Proving

• The characteristic of the master is defined by the primary standard.

• The master can then be used to prove the meter under test. Because both the master and the meter under test are at the same temperature and pressure these effects do not need to be considered in master proving.

Master Meter Proving• The master meter and the meter under

test need to be as close together as is reasonable. Long distances (50 or 60 meters) is not advisable because of possible temperature changes between the two units.

Some things to watch when master meter or volumetric proving

• System product temperatures should remain within 5 degrees C during the proving runs.

• System temperatures should be below 38 degrees C for products similar to HSD and SKO. Above this temperature, product flashing may occur affecting the calibration.

Some things to watch when master meter or volumetric proving

• Complete the proving of a meter in one session. Do not run half of the runs in the afternoon and the rest of the runs the following morning.

• Make sure the meters under test are properly filled, air bled and temperature stabilized before proving.

P.D.Meter Model : MSAA-30-P-01 Pulser Model : VS-300 Master Meter Model : MS-30-P-01P.D.Meter Sr. No. : 419 Pulser Sr.No.: 4798 Master Meter Sr.No. : 152/97Meter Element No. : 342765 Date : 24th Dec. '97 Calibrated at LCIPL

Base K-Factor = 19.30 Pulses/Liter

Master Mtr. Indicated AverageSr. Flow Rate K-Factor Master Rdg. Master Rdg. Test Rdg. Test Rdg. Meter Meter RepeatabilityNo. LPM Pulses/Liter Pulses Liter Pulses Liter Factor Factor

1 1200 19.3907 34840 1796.74 34798 1803.01 0.996522 1200 19.3907 34898 1799.73 34855 1805.96 0.99655 0.99653 0.003 1200 19.3907 35043 1807.21 35001 1813.52 0.99652

4 850 19.3950 25183 1298.43 25158 1303.52 0.996095 850 19.3950 25257 1302.24 25234 1307.46 0.99601 0.99601 0.016 850 19.3950 25220 1300.34 25199 1305.65 0.99593

7 500 19.4010 19434 1001.70 19418 1006.11 0.995618 500 19.4010 19495 1004.85 19482 1009.43 0.99546 0.99553 0.019 500 19.4010 19353 997.53 19339 1002.02 0.99551

10 150 19.4063 19392 999.26 19384 1004.35 0.9949311 150 19.4063 19350 997.10 19344 1002.28 0.99483 0.99488 0.0112 150 19.4063 19464 1002.97 19457 1008.13 0.99488

Linearity = +/- 0.09Calibrated by : Approved by :

Customer : End User : Calibration Report for Meter with Electronic PulserConsultant : Liquid Controls India Pvt. Ltd.EIL Job No.:

Some Accuracy Curves• Regulatory: Meets NIST and other international weights & measures

accuracy requirements. Meets performance requirements of USA Military Specifications